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In the programming languages I know, the function command is used to define functions. Let’s introduce the usage of function in php.
User-defined functions are also called custom functions. They are not provided by PHP and are created by programmers. Since you create such functions yourself, you can fully control these functions. Therefore, you can make a function completely according to your own needs. Runs the way you want.
1, declare function
In PHP, the method of defining functions is almost the same as in other programming languages. The following is the syntax structure of PHP function declaration:
The code is as follows | Copy code | ||||
{ //Function code code Return return value; }
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(1)function: keyword used to declare user-defined functions.
(2)function_name: The name of the function to be created. This name will be used when it is called later. The function name should be unique because PHP does not support overloading. When naming functions, you need to follow the variable naming
The same principle. But the function name cannot start with $, but the variable can.
(3)argument: The value to be passed to the function. The function can have multiple parameters, with commas between them. But the parameter items are optional, and you can not pass any parameters when calling the function.
(4)code: It is a piece of code that is executed when the function is called. If there are two or more statements, the code must be enclosed in curly brackets "{}". However, if there is only one code, then No need for braces.
代码如下 | 复制代码 |
require 'a.php'; ?> |
(5)Return: Return the value required by the calling code. Any type can be returned, including lists and objects. This causes the function to immediately end its running and transfer control back to the line where it was called.
2, parameterless function
Code func_1.php
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require 'a.php';
(2) Reference parameters. When passing by value, only a copy of the parameters is passed to the called function. However, any modification to these values within the called function will not affect the calling function The original value in . Passing by reference is actually address passing, passing the address of a variable as a parameter. Code valuechange.php
Code func_default.php truehttp: //www.bkjia.com/PHPjc/629100.html TechArticleIn the programming languages I know, the function command is used to define functions. Let’s introduce it below. About the usage of functions in php. User-defined functions are also called custom...
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